At present, a power battery (secondary battery) generally has a hard shell structure. The bare cell has a winding or laminated structure which includes anode and cathode plates and an insulating film interposed between the anode and cathode plates. As well known in the art, the winding bare cell generally has a radius of curvature in the direction of winding, and the surface where the anode and cathode tabs are located and the surface opposite to the tabs are non-rounded. The bare cell having a laminated structure has no rounded corners.
Currently, most power batteries are packaged with the two arcs of the bare cell facing the two sides of the housing, the tabs facing the top of the housing, and the surface opposite to the tabs facing the bottom of the housing. However, since the bottom of the housing is usually rounded, when the surface without round corners of the bare cell faces the bottom of the housing, it will interfere with the rounded corners around the bottom of the housing, resulting in deformation of the bare cell due to squeeze, and sometimes even resulting in short-circuit of the secondary battery when the anode and cathode plates are squeezed to contact with each other.
In addition, for the safety performance of a battery module, a power battery has installed an explosion proof valve at the bottom of the housing. The conventional power battery has only a thin insulating film for separating the bare cell from the bottom of the housing, and the bare cell almost directly contact the bottom of the housing. When the air pressure inside the bare cell causes the explosion proof valve to open during the safety performance test, such as nail penetration test, the internal pressure of the battery will still increase rapidly because there is no effective channel to guide the gas inside the bare cell to the explosion proof valve, which will lead to explosion of the housing. At the same time, the gas emitted from the explosion proof valve will carry a large amount of sparks and electrolyte, which will lead to fire after eject from the housing and mixes with air.
Furthermore, the conventional secondary battery is manufactured by injecting electrolyte into the cell from the top of the secondary battery. Part of the electrolyte is infiltrated to the anode and cathode plates through the top of the bare cell, but most of the electrolyte is directly deposited on the bottom of the housing. However, since the bottom of the bare cell is substantially in contact with the bottom of the housing, it is difficult for the electrolyte to infiltrate the anode and cathode plates upwardly, which will result in low injection efficiency.
In view of the foregoing, what is needed, therefore, is to provide a secondary battery which can solve the problems as discussed above.